Debt - Additional Information (Detail) (USD $)	1 Months Ended			12 Months Ended
	Mar. 31, 2012	Apr. 30, 2011	Feb. 28, 2009	Dec. 31, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Line of credit facility, amount outstanding				$ 13,025,000	$ 16,273,000
Line of credit facility, current borrowing capacity			30,000,000
Line of credit facility, maximum borrowing capacity		$ 35,000,000
Line of credit facility, interest rate description	LIBOR plus 1.75	LIBOR plus from 1.75% to 2.25	LIBOR plus 1 1/2	LIBOR plus 1.75
Line of credit facility, interest rate at period end	1.75%		1.50%	1.75%	1.75%
Minimum
Line of Credit Facility [Line Items]
Line of credit facility, interest rate at period end		1.75%	3.00%
Maximum
Line of Credit Facility [Line Items]
Line of credit facility, interest rate at period end		2.25%		1.962%